Indium is a wonderful metal because unlike so many soft, silvery, low-melting-point metals it's neither dangerously reactive nor toxic. It is so soft you can easily bend it, or dent it with your fingernail. Having handled both, I would say that subjectively speaking it's fairly similar to sodium in terms of feel. The big difference is that I have sensibly never touched sodium with my bare hands (it would burn them), while you could lick an indium bar without coming to harm.

I recommend indium if you want to have something quite unusual, yet safe, around: It's not a common experience to play with a metal this soft.

Indium forms an alloy with gallium that is liquid at room temperature, and is fairly non-toxic. This would be a great substitute for mercury, except it sticks to everything and stains hands, which means you can't really touch it either. This is a real shame, because it would be great fun to have a liquid metal that is safe and clean to play with. (People used to let kids play with mercury all the time, but this was not a good idea because of mercury's toxicity.)

Ingot.
Purchased by Ed from Randolph Zerr, estuff@aol.com, on eBay in May 2002. Those marks you see in the picture are from people's fingernails: This stuff is very soft!Source:eBay seller estuffContributor:Ed Pegg JrAcquired:8 May, 2002Price: $20/50 gramsSize: 1.5"Purity: >99%

Crying bars.
When you bend it, indium gives out a "cry" much like the better-known "tin cry". Neither of them is really much like a cry, as you can hear if you play the sound for this sample.

This sound file is a bit larger than most, because it's a super-high fidelity recording made in the "dead end" studio at WGBH Boston, using the finest high sensitivity microphones available, and I didn't want to lose anything by compressing it. My host family when I attended the Ig Nobel Prize ceremony, Jane and Miles, are both sound engineers at WGBH, and they kindly set up a recording session to capture this important element sound.

When Oliver Sacks came to visit me he liked these bars so much that I gave him one to take home, so there are actually only two left in the table.

Three 70g ingots.
These ingots were melted down from some thick indium wire that a guy got from Boeing. I am not sure of their purity, but will test them eventually, and the price was right.Source:eBay seller ezthirftyContributor:Theodore GrayAcquired:4 January, 2003Price: $30Size: 2"Purity: >95%

Sample from the RGB Set.
The Red Green and Blue company in England sells a very nice element collection in several versions. Max Whitby, the director of the company, very kindly donated a complete set to the periodic table table.

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

Six 70g ingots.
This is a second batch if indium ingots from the same source as the three listed above. I assume they were from the same source, melted down from some thick indium wire that a guy got from Boeing. These ones are engraved with their weight, probably just by scratching with a sharp stick: Indium is seriously soft. I am not sure of their purity, but will test them eventually, and the price was right, again.Source:eBay seller ezthirftyContributor:Theodore GrayAcquired:5 June, 2003Price: $20/eachSize: 2"Purity: >99%

Cut ingot.
This is about 3/5 of a 1kg ingot of high purity indium metal. The remainder was mainly used up making melting spoon alloy, which is 51% indium. The price of indium was very high at the time this sample as committed to the collection, but may well go down (or up), so don't take the price listed as particularly reflective of the price at any time in the future.

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.

Vacuum seal foil.
This very soft indium foil is used to create seals between glass components in high-vacuum systems. The indium is soft enough to deform into any pits and irregularities in the glass just like a rubber seal would. But unlike rubber, indium doesn't give off all sorts of vapors and leak like a sieve. ("Leak like a sieve" being a relative term: In most applications rubber would be considered airtight, but some air and moisture does still make it through, and when you're trying to create a really good vacuum it would be completely inadequate.)Source:Ethan CurrensContributor:Ethan CurrensAcquired:30 October, 2006Text Updated:19 November, 2007Price: DonatedSize: 2"Purity: 99%

Element coin.
Dave Hamric sells element samples under the name Metallium. He's developed a line of coins struck out of various common and uncommon metals: They are quite lovely, and very reasonably priced, considering the difficulty of creating some of them.

Indium is extremely soft, so this coin needs to be protected from curious people with thumbnails.

Here is the back side of this coin (click either picture to see it larger):
Click the Sample Group link below to see many other coins made of various elements, or click the link to his website above if you want to buy one like this.Source:Dave HamricContributor:Theodore GrayAcquired:1 December, 2006Text Updated:14 January, 2007Price: $16Size: 0.75"Purity: >99%Sample Group:Coins

Indium foil.
Indium foil like this is typically used in high-vacuum systems to form a seal between glass components. It is soft enough to squeeze into the glass surfaces and form a perfect seal. Unlike rubber, it does not give off gases of its own, or allow air to diffuse through slowly.Source:eBay seller assetrecoveryctsystemsContributor:Theodore GrayAcquired:24 February, 2007Text Updated:29 January, 2009Price: $17/20Size: 1.5"Purity: >99%

Indium rod.
This is very, very high purity indium, and the surface texture comes not from bending (as one might do to hear the crackling sound it makes) but rather from etching to show the crystal structure.Source:Juan JimenezContributor:Juan JimenezAcquired:2 December, 2007Text Updated:7 December, 2007Price: DonatedSize: 2.5"Purity: 99.99999%

Spool of indium wire.
This is one of several spools of indium wire I got on eBay for about half the market price at the time. My theory is that the reason it went so cheap is that the seller listed it as 63.5 ounces, while the market price of indium is generally quoted in kilograms. Nobody did the math.
See, there are some advantages to living in a country with a dysfunctional education system: More chances to take advantage of the innumerate. Oh, why bother pretending, this place is going to the dogs, what more proof do you need than below-market indium?Source:eBay seller halide2Contributor:Theodore GrayAcquired:8 March, 2008Text Updated:8 March, 2008Price: $765/4Size: 4"Purity: 99.99%

Indium foil.
Indium is often used to form air-tight seals between glass components because it is soft enough to mold itself to the shape of the glass, and because unlike rubber or other organic seal materials it is really 100% gas-tight and it doesn't release volatile compounds of its own. For high-vacuum applications only glass and metal can come in contact with the vacuum because anything else would either out-gas or leak.Source:Ethan CurrensContributor:Ethan CurrensAcquired:14 June, 2008Text Updated:14 June, 2008Price: DonatedSize: 2"Purity: 99.9%

Invisible wires on screen.
You can't see the indium tin oxide wires connecting the individual pixels in this old cell phone screen, because they are transparent. That is the whole point of using indium tin oxide.Source:Theodore GrayContributor:Theodore GrayAcquired:17 April, 2009Text Updated:17 April, 2009Price: DonatedSize: 2"Purity: <5%

Field's metal.
Field's metal is a low-melting-point alloy, which will melt in hot water. It's named after Simon Quellen Field, who runs scitoys.com, a great site for educational and scientific toys and kits. He sells this alloy in the form of lengths of metal-filled plastic tubing, which you can easily melt or cut it out of.Source:Simon Quellen FieldContributor:Simon Quellen FieldAcquired:13 February, 2007Text Updated:14 February, 2007Price: DonatedSize: 5"Composition:InBiSn

Field's metal crust.
Nice smooth samples of the elements are boring if you ask me. They just don't make for interesting photographs, and the more symmetrical they are the less interesting it is to see them rotated around a full circle (which is how I photograph all new samples these days). This crust of Field's Metal (named after Simon Quellen Field, who runs scitoys.com) is a perfect example: I scraped it from the side of a jar at Simon's house, and it's got a much more interesting texture than a plain melted piece. Plus if you look at the rotation video you can see a completely different kind of surface on the other side. Source:Simon Quellen FieldContributor:Simon Quellen FieldAcquired:4 September, 2007Text Updated:6 September, 2007Price: DonatedSize: 1"Composition:InBiSn

Insane mineral capsules.
These minerals capsules are called "Immune Boost 77", from Morningstar Minerals. They are either being incredibly honest, or they really don't understand what they're saying when they list what amounts to nearly the entire periodic table on the label, as the "trace minerals" they contain.

Some of them are just silly, like thulium, which has absolutely no biological function. Others are a bit scarier, like thallium and thorium that are deadly poisons, and tellurium, which makes you smell of rotten onions for weeks.

Basically what they've done is list everything that occurs in even trace amounts in mixed monazite sand, which is kind of what the stuff inside looks like. The only reason they aren't seriously harmful (I assume) is that most of these are not actually present in any meaningful quantity.

My attention is drawn to these and other similar mineral supplements every time I decide to see if anything interesting has popped up on eBay for one or another of the obscure rare earths. Generally speaking if you search eBay for those guys you get very little of interest unless you turn on the option to search the text of the item description as well as the titles. Then you get lots of trace mineral supplements that one can only hope don't actually contain them.

Himalayan sea salt.
There is a list of 84 elements that seems to pop up repeatedly in the ingredient lists of "natural" mineral products, supplements, pills, and the like. Even, it turns out, in salt. Here then is the list of minerals claimed to be found in all-natural organic Himalayan sea salt:

I wish someone would tell these people that, for example, neptunium and plutonium do not occur in nature at all, let alone in salt. Unless, I suppose, if you count nuclear fallout as a "natural" source of ingredients.
What bothers me most is what this says about the level of scientific literacy, both of the people selling the stuff, and the people buying it. Does no one actually read the list? Or do they read it an not realize how preposterous it is? It's enough to make you despair for the future of mankind.
Pretty salt, though.Source:eBay seller saltwondersContributor:Theodore GrayAcquired:28 March, 2009Text Updated:4 April, 2009Price: $15Size: 0.25"Composition:NaClSbCsDyErEuGdHfHoInLaLuNdPrSmScThTlTeTbTmYbY